A clasp responding to the generic definition hereinabove is described in patent document EP-A-0 509 938. In this document, the clasp comprises two arms which are hinged to bracelet strands at one of their ends and at their other end to ends of two branches parallel to a central element in stretcher form. The central element exhibits two notches having a form and dimensions corresponding to those of the arms so that the arms are entirely included within the notches in the closed position of the bracelet. Latching the bracelet in its closed position is assured by a snap system. In order to assure such latching, the end of the arm which is attached to the strand exhibits a beak, one of the parts of which exhibits a groove which cooperates with a cylindrical element or bridge connecting the branches after they have been elastically engaged onto this latter.
This latching system has the drawback of being subject to rapid wear which has as result that the clasp is no longer effectively assured after a certain number of openings and closings.
Such rapid wear also leads to considerable variations in the opening and closing forces which is unsatisfactory for the user, such forces being furthermore dependent on the nature of the materials used for forming the clasp.
To this is added the inherent play existing between the groove and the cylindrical element which gives an impression of indifferent quality to this latching system.
For the rest, such clasp is relatively difficult to form with precision since it requires numerous mechanical operations, in particular touch up machining following stamping out of the branches and the arms and the adjustment of the beak with the bridge prior to assembly of the clasp in order to obtain an acceptable opening force and closing force.